LED lighting apparatus and method for manufacturing the same

ABSTRACT

To provide an LED lighting apparatus and a method for manufacturing the same that can improve the bonding strength between an aluminum substrate and a printed wiring substrate. An LED lighting apparatus and a method for manufacturing the same, the LED lighting apparatus includes an aluminum substrate, a plurality of reflectivity-enhanced layers formed on the aluminum substrate, an LED device bonded on said plurality of reflectivity-enhanced layers, a printed wiring substrate bonded onto a region on the aluminum substrate other than a region where the plurality of reflectivity-enhanced layers are formed, a wire for connecting between the printed wiring substrate and the LED device, a frame member formed so as to surround said LED device, and a phosphor resin deposited over a region inside the frame member.

CROSS-REFERENCES TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 14/686,909, filed on Apr. 15, 2015 that claims benefit of JP2014-89301, filed on Apr. 23, 2014, the entire content of theapplications are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to an LED lighting apparatus and a methodfor manufacturing the same, and more specifically to an LED lightingapparatus constructed by mounting an LED device onto an aluminumsubstrate and a method for manufacturing such an LED lighting apparatus.

BACKGROUND ART

In recent years, LED devices as semiconductor devices have come intowide use in illumination and other applications due to their long lifeand excellent driving characteristics as well as their compact size,good luminous efficacy, and crisp and bright color emission.

To construct a lighting apparatus for illumination purposes, it is knownto apply specular treatment such as vapor deposition or anodizingtreatment to an aluminum surface and then mount an LED device thereon sothat the light emitted from the LED device can be reflected efficiently(for example, refer to Japanese Unexamined Patent Publication No.2007-109701).

SUMMARY

However, there has been the problem that when a wiring substrate,electrodes, etc., that are connected to the LED devices by being bondedto the specular surface by means of an adhesive sheet or the like, thewiring substrate, etc., may delaminate at the layers formed by thespecular treatment, because the adhesion between the layers formed bythe specular treatment is insufficient.

There has also been the problem that when the aluminum substrate issubjected to thermal expansion and thermal shrinkage due to changes inambient temperature, interlayer delamination may occur between thelayers formed by the specular treatment and, in this case also, thewiring substrate, etc., may become delaminated.

Accordingly, it is an object of the present invention to provide an LEDlighting apparatus and a method for manufacturing the same that cansolve the above problems.

It is also an object of the present invention to provide an LED lightingapparatus and a method for manufacturing the same that can improve thebonding strength between an aluminum substrate and a printed wiringsubstrate.

An LED lighting apparatus includes an aluminum substrate, a plurality ofreflectivity-enhanced layers formed on the aluminum substrate, an LEDdevice bonded on the plurality of reflectivity-enhanced layers, aprinted wiring substrate bonded onto a region on the aluminum substrateother than a region where the plurality of reflectivity-enhanced layersare formed, a wire for connecting between the printed wiring substrateand the LED device, a frame member formed so as to surround the LEDdevice, and a phosphor resin deposited over a region inside the framemember.

Preferably, in the LED lighting apparatus, the printed wiring substrateis bonded on a roughened surface region formed outside the region wherethe plurality of reflectivity-enhanced layers are formed.

Preferably, in the LED lighting apparatus, the plurality ofreflectivity-enhanced layers comprise an adhesive layer, a reflectivelayer, and an enhanced. reflectivity layer.

A method for manufacturing an LED lighting apparatus includes the stepsof forming a mask on an aluminum substrate on which a plurality ofreflectivity-enhanced layers are formed, forming a roughened surfaceregion on the aluminum substrate by removing the plurality ofreflectivity-enhanced layers everywhere except where the mask is formed,bonding a printed wiring substrate on the roughened surface region,bonding an LED device on the plurality of reflectivity-enhanced layersfrom which the mask has been removed; connecting the LED device to theprinted wiring substrate by a wire, and depositing a phosphor resin overa region inside a frame member formed so as to surround the LED device.

According to the LED lighting apparatus and the method for manufacturingthe same as stated above, the printed wiring substrate does not becomedelaminated from the aluminum substrate, and thus, an LED lightingapparatus with high reliability can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantageous of the present lighting apparatus willbe apparent from the ensuing description, taken in conjunction with theaccompanying drawings, in which:

FIG. 1A is a top plan view of an LED lighting apparatus 1 according tothe present invention.

FIG. 1B is a cross-sectional view taken along line AA′ in FIG. 1A.

FIG. 2A is a diagram (part 1) for explaining a manufacturing process forthe LED lighting apparatus 1.

FIG. 2B is a diagram (part 1) for explaining a manufacturing process forthe LED lighting apparatus 1.

FIG. 2C is a diagram (part 1) for explaining a manufacturing process forthe LED lighting apparatus 1.

FIG. 2D is a diagram (part 1) for explaining a manufacturing process forthe LED lighting apparatus 1.

FIG. 2E is a diagram (part 1) for explaining a manufacturing process forthe LED lighting apparatus 1.

FIG. 3A is a diagram (part 2) for explaining a manufacturing process forthe LED lighting apparatus 1.

FIG. 3B is a diagram (part 2) for explaining a manufacturing process forthe LED lighting apparatus 1.

FIG. 3C is a diagram (part 2) for explaining a manufacturing process forthe LED lighting apparatus 1.

FIG. 3D is a diagram (part 2) for explaining a manufacturing process forthe LED lighting apparatus 1.

FIG. 4A is a diagram for explaining a manufacturing method of anotherLED lighting apparatus 2.

FIG. 4B is a diagram for explaining a manufacturing method of anotherLED lighting apparatus 2.

FIG. 4C is a diagram for explaining a manufacturing method of anotherLED lighting apparatus 2.

FIG. 4D is a diagram for explaining a manufacturing method of anotherLED lighting apparatus 2.

DESCRIPTION

An LED lighting apparatus according to the present invention and amethod for manufacturing the same will be described below with referenceto the drawings. It should, however, be noted that the technical scopeof the present invention is not limited by any particular embodimentdescribed herein but extends to the inventions described in the appendedclaims and their equivalents.

FIG. 1A is a top plan view of the LED lighting apparatus 1 according tothe present invention, and FIG. 1B is a cross-sectional view taken alongline AA′ in FIG. 1A.

The LED lighting apparatus 1 comprises an aluminum substrate 10, aprinted wiring substrate 18, a frame member 19, LED devices 20, and aphosphor resin 30, and is installed to a lighting fixture by means ofguiding holes 40 provided in edge portions.

In a device mounting region 45 enclosed by the frame member 19 formed ina substantially circular shape by depositing a silicone resin, there areformed an adhesive layer 11, a reflective layer 12, and an enhancedreflectivity layer 13 one on top of another on the aluminum substrate 10for enhanced reflection.

The adhesive layer 11 is an anodized aluminum layer. The reflectivelayer 12 is an Ag or Al deposited layer whose reflectivity is 90% orhigher. The enhanced reflectivity layer 13 is formed from a stack of atleast one SiO₂ layer and at least one TiO₂ layer having a greaterrefractive index than SiO₂. A stack of an Al₂O₃ layer and a TiO₂ layerhaving a greater refractive index than Al₂O₃ may be used instead of thestack of the SiO₂ and TiO₂ layers. The enhanced reflectivity layer 13 isprovided in order to enhance reflectivity.

In the device mounting region 45, the LED devices 20 arranged in threegroups, each of 12 LED devices connected in series, are connected inparallel by gold wires 22 between electrodes 16-1 and 16-2 formed on theprinted wiring substrate 18. Each LED device 20 is bonded by a diebonding material 21 directly to the reflectivity-enhanced surface of thealuminum substrate 10. The LED device 20 emits light when a prescribedvoltage is applied between the electrodes 16 a and 16 b formed on theprinted wiring substrate 18.

The phosphor resin 30 for protecting the LED devices 20 is formed insidethe frame member 19 so as to enclose the LED devices 20. A transparentepoxy resin or silicone resin is used to form the phosphor resin 30. Thephosphor resin 30 contains phosphors dispersed through the resin. Sincethe phosphors absorb a portion of the blue light emitted from the LEDdevices 20 and produce yellow light by wavelength conversion, the LEDlighting apparatus 1 emits white light with the yellow light mixing withthe blue light. The phosphor resin 30 may also contain a diffusingmaterial for uniformly diffusing the light emitted from the LED devices20.

A roughened surface region 46 not treated for enhanced reflection buttreated by roughening the aluminum surface is formed on the aluminumsubstrate 10 so as to surround the device mounting region 45. Theprinted wiring substrate 18 is bonded on the roughened surface region 46by means of an adhesive sheet 14. The printed wiring substrate 18includes a base 15 and a resist 17 in addition to the electrodes 16-1,16-2, etc.

In the device mounting region 45 treated for enhanced reflection withthe plurality of layers, the adhesion between the layers isinsufficient; therefore, if the printed wiring substrate 18 is bonded onthis. region, the printed wiring substrate 18 may become delaminatedfrom the aluminum substrate 10 due to interlayer delamination.Furthermore, when the aluminum substrate is subjected to thermalexpansion or shrinkage due to changes in ambient temperature, interlayerdelamination may also occur, causing the printed wiring substrate 18 todelaminate from the aluminum substrate 10. By contrast, in the LEDlighting apparatus 1, since the printed wiring substrate 18 is bonded,not on the device mounting region 45 treated for enhanced reflection,but on the roughened surface region 46 by using the adhesive sheet 14,the printed wiring substrate 18 can be firmly bonded to the aluminumsubstrate 10. Furthermore, since the printed wiring substrate 18 doesnot become delaminated from the aluminum substrate 10 due to the thermalhistory given to the LED lighting apparatus 1 when, for example,installing the LED lighting apparatus 1 to a lighting fixture, itbecomes possible to manufacture a package with high reliability.

FIGS. 2 and 3 are diagrams for explaining a manufacturing process forthe LED lighting apparatus 1.

First, as shown in FIG. 2A, a reflectivity-enhanced aluminum plate 10′is prepared. In this example, Miro 20.7t manufactured by Anorad was usedas the reflectivity-enhanced aluminum plate 10′. Thereflectivity-enhanced aluminum plate 10′ has a multilayered structure inwhich the adhesive layer 11 of anodized aluminum, the reflective layer12 of an Al deposited film, and the enhanced reflectivity layer 13formed from a stack of SiO₂ and TiO₂ layers (at least one each) aredeposited one on top of another on the aluminum substrate 10. If thereflective layer 12 is formed from an Ag deposited film, thereflectivity will improve, but since it is susceptible to corrosion, anAl deposited film is used here.

Next, as shown in FIG. 2B, the guiding holes 40 are opened through thealuminum plate 10′ by using a drilling machine.

Next, as shown in FIG. 2C, a photosensitive dry film 50 is laminated tothe surface of the aluminum plate 10′ by using a laminator. In thisexample, an alkaline-developing dry film “PHOTEC (registered trademark)H-7025” manufactured by Hitachi Chemical was used as the photosensitivedry film 50.

Next, as shown in FIG. 2D, a negative film 51 for masking the devicemounting region 45 is laminated by a vacuum onto the photosensitive dryfilm 50, and is exposed to ultraviolet radiation B to cure only theportion of the photosensitive dry film 50 that masks the device mountingregion 45. Then, as shown in FIG. 2E, the exposed photosensitive dryfilm 50 is developed using a developing solution, thus forming a mask50′ on the device mounting region 45. A 1% alkaline solution was used asthe developing solution.

In the steps shown in FIGS. 2D and 2E, the mask 50′ has been formed bywet processing which involves developing the photosensitive dry film 50.Alternatively, a rubber-based ink such as a strippable solder resist(peel coat) may be applied over the device mounting region 45 by screenprinting, and then thermally cured to form the mask 50′.

Next, as shown in FIG. 3A, particles C are sprayed at high speed by sandblasting, thereby removing the portions of the adhesive layer 11,reflective layer 12, and enhanced reflectivity layer 13 that lie outsidethe region covered by the mask 50′, and the exposed surface of thealuminum substrate 10 is roughened to form the roughened surface region46. In the step shown in FIG. 3A, ice blasting which uses ice particlesmay be employed instead of sand blasting. Ice blasting is preferable tosand blasting, because the latter tends to leave a residue.

In the step shown in FIG. 3A, the roughened surface region 46 has beenformed by a physical means such as sand blasting (or ice blasting), butthe roughened surface region 46 may be formed chemically by using anetching solution of sulfuric acid or hydrochloric acid. When chemicallyforming the roughened surface region 46, it is desirable to laminate thephotosensitive dry film 50 on both sides of the aluminum plate 10′.Further, instead of using the physical means, the roughened surfaceregion 46 may be formed electrically by plasma processing.

Next, as shown in FIG. 3B, the mask 50′ is removed by using an alkalinesolution.

Next, as shown in FIG. 3C, the printed wiring substrate 18 with theadhesive sheet 14 tentatively attached thereto is registered withrespect to the aluminum substrate 10, and is laminated to the roughenedsurface region 46 under prescribed temperature and pressure. The printedwiring substrate 18, before lamination, comprises the base 15, theelectrodes 16-1, 16-2, etc., and the resist 17, and guiding holes aboutthe same size as the guiding holes formed in the aluminum plate 10′ areformed in respectively corresponding positions. Next, using the diebonding material 21, each LED device 20 is bonded on the device mountingregion 45. Then, the LED devices 20 are connected to each other as wellas to the electrodes 16-1 and 16-2 by using the gold wires 22.

Next, as shown in FIG. 3D, using a dispenser, a silicone resin isdeposited in a substantially circular shape around the device mountingregion 45 and cured to form the frame member 19. The height of the framemember 19 is preferably in the range of 100 μm to 600 μm. Next, using adispenser, the phosphor resin 30 is deposited inside the frame member 19and cured to complete the manufacturing of the LED lighting apparatus 1.A transparent silicone resin may be molded over the phosphor resin 30.

FIG. 4 is a diagram for explaining a manufacturing method of another LEDlighting apparatus 2.

First, as shown in FIG. 4A, an aluminum substrate 10 not treated forenhanced reflection is prepared. In this example, a general-purposealuminum alloy 55052-01.2t available from Sumitomo Light MetalIndustries was used to form the aluminum substrate 10.

Next, as shown in FIG. 4B, the guiding holes 40 are opened through thealuminum substrate 10 by using a drilling machine.

Next, as shown in FIG. 4C, an adhesive layer 61 of anodized aluminum, areflective layer 62 of an Ag deposited film, and an enhancedreflectivity layer 63 formed from a stack of SiO₂ and TiO₂ layers (atleast one each) are deposited one on top of another only on a regioncorresponding to the device mounting region 45.

Next, as shown in FIG. 4D, the printed wiring substrate 18 with theadhesive sheet 14 tentatively attached thereto is registered withrespect to the aluminum substrate 10, and is laminated under prescribedtemperature and pressure to the region where the stack of the adhesivelayer 61, reflective layer 62, and enhanced reflectivity layer 63 is notformed. The printed wiring substrate 18, before lamination, comprisesthe base 15, the electrodes 16-1, 16-2, etc., and the resist 17, andguiding holes about the same size as the guiding holes formed in thealuminum plate 10′ are formed in respectively corresponding positions.Next, using the die bonding material 21, each LED device 20 is bonded onthe device mounting region 45. Then, the LED devices 20 are connected toeach other as well as to the electrodes 16-1 and 16-2 by using the goldwires 22.

Next, using a dispenser, a silicone resin is deposited in asubstantially circular shape around the device mounting region 45 andcured to form the frame member 19. The height of the frame member 19 ispreferably in the range of 100 μm to 600 μm. Next, using a dispenser,the phosphor resin 30 is deposited inside the frame member 19 and curedto complete the manufacturing of the LED lighting apparatus 2. Atransparent silicone resin may be molded over the phosphor resin 30.

The only difference between the LED lighting apparatus 1 shown in FIGS.1 to 3 and the LED lighting apparatus 2 shown in FIG. 4D is the presenceor absence of the roughened surface region 46, which is present in theLED lighting apparatus 1 but is absent in the LED lighting apparatus 2which instead has the untreated surface of the aluminum substrate 10exposed.

In the LED lighting apparatus 2 also, since the printed wiring substrate18 is bonded, not on the device mounting region 45 treated for enhancedreflection, but on the surface of the aluminum substrate 10 by using theadhesive sheet 14, the printed wiring substrate 18 can be firmly bondedto the aluminum substrate 10. Furthermore, since the printed wiringsubstrate 18 do not delaminate from the aluminum substrate 10 due to thethermal history given to the LED lighting apparatus 2 when, for example,installing the LED lighting apparatus 2 to a lighting fixture, it ispossible to manufacture a package with high reliability.

The preceding description only illustrates and describes exemplaryembodiments of the present lighting apparatus. It is not intended to beexhaustive or to limit the invention to any precise form disclosed. Itwill be understood by those skilled in the art that various changes maybe made and equivalents may be substituted for elements thereof withoutdeparting from the scope of the invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the invention without departing from the essentialscope. Therefore, the invention is not limited to the particularembodiment disclosed as the best mode contemplated for carrying out thisinvention, but the invention will include all embodiments falling withinthe scope of the claims. The invention may be practiced otherwise thanis specifically explained and illustrated without departing from itsspirit or scope.

What is claimed is:
 1. A method for manufacturing an LED lightingapparatus, comprising the steps of: forming a mask on a device mountingregion on a multilayered structure having an aluminum substrate, anadhesive layer, a reflective layer, and an enhanced reflectivity layer;forming a roughened surface region on said aluminum substrate byremoving portions of said adhesive layer, said reflective layer, andsaid enhanced reflectivity layer surrounding said mask; bonding aprinted wiring substrate on said roughened surface region; removing saidmask and bonding an LED device on said device mounting region;connecting said LED device to said printed wiring substrate by a wire;and depositing a phosphor resin over a region inside a frame memberformed so as to surround said LED device.
 2. The method according toclaim 1, wherein said enhanced reflective layer includes SiO₂, TiO₂,Al₂O₃, or a combination thereof.